1. Field of the Invention
The present invention is generally related to the operation of grease guns. More particularly, the present invention pertains to a system and method for refilling the reservoir of a grease gun.
2. Introduction
Grease guns utilize a reservoir, for example, tubes or cartridges, to hold grease while a plunger, pull rod mechanism, or other similar mechanism forces grease from the reservoir to a dispenser. When the gun runs out of grease, the tube in reservoir is usually replaced. Replacing the reservoir generally means removing the spent tube or cartridge and replacing it with a new one. Replacing the reservoir also means that one comes into contact with grease residue contained in the old reservoir or grease from the new reservoir resulting in an unwanted mess. Moreover, disposal of the spent reservoir becomes an environmental concern because of the remaining grease residue. Though the grease gun has been improved over the years, grease residue resulting from the process of switching from an old grease reservoir to a new grease reservoir remains an issue.
For example, to remove a spent tube of grease, one must first grasp the T-bar that is fixed to the outer end of the pull rod mechanism at the bottom outer portion of the grease reservoir. In drawing the pull rod out through the bottom of the grease reservoir, the wiper piston is also pulled back through the spent tube of grease due to the design of the pressure mechanism of the grease gun. The pressure mechanism is made up of the pull rod with a T-handle affixed to the outer end portion for one to grab onto. The piston rod runs the full length of the grease reservoir. A compression spring runs the full length inside the grease reservoir. The piston rod slides through a slotted hold in the bottom of the grease reservoir and traverses fully through the center of the compression spring inside the grease reservoir. The piston rod slides through the center of the wiper piston and has its end buttoned off so that it cannot slide backward out of the piston. This design enables one to draw the wiper piston back through the spent grease tube and compress the compression spring. The piston rod being drawn out completely compresses the compression spring and places the wiper piston at the bottom of the spent tube of grease. To hold the pressure of the compression spring in this compressed condition while replacing the spent tube of greases causes one to rotate the piston rod sideways into the slot at the bottom of the grease reservoir where it engages a machined ring in the piston rod below the wiper piston to reveal itself outside the bottom of the grease reservoir.
Next, one needs to unscrew the grease reservoir from the head of the grease gun. Removal reveals the outer ring of the spent grease tube in the grease reservoir. The spent grease tube can now be removed as the piston rod assembly has been fixed at the bottom of the grease reservoir.
After removing the spent tube, a full tube of grease is inserted into the grease reservoir housing assembly. Fully inserting the new tube of grease into the reservoir housing bases the grease in the bottom of the new tube of grease to come into contact with the wiper piston being held in place by the pull rod. The grease reservoir is rethreaded into the head of the grease gun. After securing the two operating members together, the pull rod is rotated out of the slot assembly at the bottom of the grease reservoir. The pressure generated by the compression spring is fully transferred to the wiper piston that is in contact with new grease in the tube. The pull rod must be pushed into and through the new grease in the new tube so that the T-bar handle shows at the bottom of the grease reservoir. As grease is consumed, the wiper piston continues to slide along the pull rod being pushed by the compression spring and applying pressure to the grease in the tube to force it towards the head of the grease gun where the grease engages with the gun's pumping mechanism.
As described above, changing grease tubes in grease guns involve multiple steps and a mess that needs to be cleaned up. What is needed is a system that eliminates or partially eliminates the need for a pull rod mechanism and its associated functionality.